Nowadays, when extracting common indoor footprint images on hard and flat ground, such as floor tiles and ground tiles, or a table surface, people still use the traditional manual operation methods with cameras and lights. There is still not an integrated portable device designed for the specific purpose of extracting footprints. Also, the present method of crime-scene footprint photography and extraction methods mainly utilize police floodlights from different angles and cameras to collect footprint images twice. The images collected for the first time show the footprint and its trace carrier, while those collected for the second time show the trace carrier without a footprint. Because all of the images have to be photographed manually on the scene, and the images vary when taken by different operators; there are common problems such as follows:
1. Tilted photographing angle causes the deformation of photographed footprint images;
2. The normal indoor lighting on the scene also makes the images of floor patterns clear, which interferes with effective footprint imaging;
3. Because manually operated by operators, the footprint image area has to be photographed with cameras at least twice, it is hard to photograph the images twice from exactly the same location. All of the abovementioned problems can interfere with the normal footprint image information, reduce the footprint image quality, and bring obstacles to recognition and analysis at a later stage.
The present application aims to overcome the shortcomings of the existing technology, and provides a crime-scene footprint photography and extraction method and extraction device.
The present application adopts the following technical schemes:
A crime-scene footprint image photography and extraction method includes the following steps:
S1: Exposing under an oblique light source, and photographing a part of or an entire illuminated area of said oblique light source from a fixed angle to obtain a first image, said first image contains a part of or an entire image of a footprint and a trace carrier image of said footprint;
S2: Exposing under a diffuse reflected light source, and photographing a part of or an entire illuminated area of said diffuse reflected light source from a fixed angle to obtain a second image, said second image contains an image of said trace carrier without any footprints;
S3: Analyzing said first image's brightness component V1 and said second image's brightness component V2, and divide said first image's brightness component V1 by said second image's brightness component V2 to produce their brightness distribution ratio V3;
S4: Extracting a third image corresponding to said brightness distribution ratio V3, said third image only contains an image of said footprint.
Preferred: Before said first image's brightness component V1 and said second image's brightness component V2 are obtained, converting said first image and said second image into HSV mode.
Preferred: In an oblique light illuminating environment, the intersection angle α between said oblique light and said footprint's trace carrier ranges between 0°≤α≤10°.
Preferred: Said first image and said second image share the same photographing area.
Preferred: Said oblique light is formed from at least two light sources located on both sides along said footprint's width direction, said oblique light sources' length direction is consistent with said footprint's length direction; said oblique light sources can compensate each other to illuminate entire said footprint.
Preferred: Said oblique light sources that form said oblique light, are formed in a strip structure.
Preferred: Said oblique light sources that form said oblique light, are formed with collimating lens or the collimating lens system.
Preferred: In said diffuse reflected light source illuminating environment, said diffuse reflected light is emitted by area light sources, said diffuse reflected light is formed from at least two said area light sources, said two area light sources are located on both sides of said footprint's width direction and said two area light sources' length direction is consistent with said footprint's length direction.
Preferred: Said oblique light source and said diffuse reflected light source alternatively illuminate a photographing area.
Preferred: Said oblique light sources and said diffuse reflected light sources are formed from white light sources.
Preferred: Said intersection angle β between a diffuse reflector used to form said diffuse reflected light and said trace carrier's surface ranges between 45°<β<90°.
A footprint image extraction device includes:
A first extraction module, is used to photograph a part of or an entire oblique light sources illuminated area to obtain a first image when exposed under said oblique light sources, said first image contains a part of or an entire image of a footprint, and an image of a trace carrier of said footprint;
A second extraction module, is used to photograph a part of or an entire diffuse reflected light sources illuminated area to obtain a second image, said second image contains an image of said trace carrier;
An analysis module, is used to analyze said first image's brightness component V1 and said second image's brightness component V2, and divide said first image's brightness component V1 by said second image's brightness component V2 to produce their brightness distribution ratio V3;
An extraction module, is used to extract a third image corresponding to said brightness distribution ratio V3, said third image only contains said footprint's image.
Preferred, including a conversion module, is used to convert said first image and said second image into HSV mode, before said first image's brightness component V1 and said second image's brightness component V2 are obtained.
Benefits from adopting the technical scheme of the present application are: The present application involves an on-scene footprint image photography and extraction method and extraction device that can photograph the image of a footprint and their trace carriers in the oblique light from a fixed angle, and in the diffuse reflected light environment, photograph the image of the trace carrier without the footprint from a fixed angle. The obtained two images can be compared and reduced to produce the footprint's image, Then removes the footprint trace carrier image, so as to display clear and cognizable footprint images only; Because the two images are photographed from the same location with the same angle, the footprint images obtained through calculation are more accurate. In addition, the on-scene footprint photography and extraction method provided in this application is simple, effective and rapid.